The invention relates generally to x-ray tubes and, more particularly, to a method and apparatus for creating an improved braze in x-ray tube components.
X-ray systems typically include an x-ray tube, a detector, and a gantry to support the x-ray tube and the detector. In operation, an imaging table, on which an object is positioned, is located between the x-ray tube and the detector. The x-ray tube typically emits radiation, such as x-rays, toward the object. The radiation typically passes through the object on the imaging table and impinges on the detector. As radiation passes through the object, internal structures of the object cause spatial variances in the radiation received at the detector. The detector then processes the received data, and the system translates the radiation variances into an image, which may be used to evaluate the internal structure of the object. One skilled in the art will recognize that the object may include, but is not limited to, a patient in a medical imaging procedure and an inanimate object as in, for instance, a package in a computed tomography (CT) package scanner.
X-ray tubes include a rotating anode structure for the purpose of distributing heat generated at a focal spot. The anode is typically rotated by an induction motor having a cylindrical rotor built into a cantilevered axle that supports a disc-shaped anode target and an iron stator structure with copper windings that surrounds an elongated neck of the x-ray tube. The rotor of the rotating anode assembly is driven by the stator. An x-ray tube cathode provides a focused electron beam that is accelerated across a cathode-to-anode vacuum gap and produces x-rays upon impact with the anode. Because of the high temperatures generated when the electron beam strikes the target, it is necessary to rotate the anode assembly at high rotational speed.
X-rays may be produced when high-speed electrons are decelerated when directed from the cathode to the target substrate via an electrical potential difference therebetween. The electrons impact a target track material at a focal point and x-rays emit therefrom. The x-ray tube includes a frame, typically constructed from stainless steel, and has an x-ray window formed therein. The x-ray window is typically made from beryllium, or other low-atomic number material. X-rays are emitted through the beryllium window toward a detector array. The x-ray tube may also include a collector attached to a perimeter of the beryllium window at an interface, wherein the collector absorbs stray electrons from the cathode or the target and conducts heat away from the interface. The collector is typically attached to the beryllium window using a brazing process.
Brazing and soldering are commonly used methods for joining two parts involving heating a fusible material, causing it to melt and wet both parts, and allowing the material to cool and bond the parts. However, diffusion and alloying between the fusible material and the parts being joined may result in formation of brittle intermetallic compounds, sometimes referred to as Laves phase intermetallics, which can weaken the braze joint and cause early life failure of the x-ray tube.
Therefore, it would be desirable to have a method for joining two parts, such as a beryllium window and an electron collector, having improved integrity and hermeticity therebetween.